Doulton W9223002 UltraCarb OBE Ceramic Filter The Doulton W9223002 UltraCarb Filter features a Sterasyl ceramic outer shell and carbon block core with ATS resin W9223002 cleanable filter elements are designed to remove suspended solids, pathogenic bacteria, hydrogen sulphide, and lead At the heart of every Doulton ceramic filter is the "Sterasyl" silver impregnated ceramic micro filter